This invention relates to agitator means for tower type abrasion mills, the agitator means having an agitating blade of a continuous screw shape.
FIG. 1 shows an example of a conventional tower type abrasion mill which is operated in a wet system. Upon pieces of ore being fed at A into cylindrical tower 8, water being supplied continuously into the tower, and milling operation being started by rotation of agitating blade 20 of a screw shape by means of motor 5, the ore within tower 8 is drawn up by agitating blade 20 and an up-and-down motion of the ore is repeated. Then, the ore, during the repeated up-and-down motion, is abraded mainly by mutual friction between the pieces of ore to produce fine particles. The particles thus produced are transported through pipe 6 by means of overflowing water to an elutriation tank not shown in the drawings, and are gathered as the product. On the other hand, water drawn from the bottom of said elutriation tank is fed back through pipe 7 into tower 8.
Agitation blade 20 which has been worn out by repeated operations must be repaired or exchanged so that further proper operations of the mill can be continued. Works for repairing an agitation blade of a shape of a screw is a considerable heavy task containing repeated cutting and welding of steel plates so as to provide again for such portions which have been worn out of the blade the blade shape exactly similar to the original one. Moreover, in most cases in which the blade had a lining of hard rubber or the like material, the blade must be lined anew after the welding work has been finished. Accordingly, loss caused by such a repair is very large due to large costs of the repair work and a long term of work stoppage. And, such a circumstances with respect to a tower type abrasion mill operated in wet system as stated above can also be applied to such a mill operated in dry system.